The invention concerns a cooling system for cooling sleeves fixed to a carrier plate, by means of a fluid which is passed from a fluid inlet to a fluid outlet by way of fluid conduits supported by means of the carrier plate, wherein belonging to the fluid conduits are main supply conduits and supply conduits which extend approximately transversely with respect thereto, the latter supply conduits extending in mutually parallel relationship and arranged in pairs in the carrier plate and being connected to a row of sleeves by way of intake and discharge conduits, wherein the row of sleeves is so disposed between the supply conduits of a pair that each sleeve is connected to both supply conduits.
It is known for drinking water to be supplied to the end consumer in bottles comprising more or less transparent plastic material, in particular PET. As is known those PET bottles are blow-moulded from preforms which in turn are injection moulded from polyethylene terephthalate (PET). The PET bottles and correspondingly the preforms of PET are required in large numbers and are produced using correspondingly powerful machines. After the injection moulding procedure the preforms have to be sufficiently cooled in order to permit processing thereof after the injection moulding procedure without damage to the preforms.
In known injection moulding machines the cooling operation is effected by way of sleeves which are fixed to a carrier plate in large numbers. Such tools are known for example from EP-B2-0 283 644. In practice the fluid used is cooling water which is fed to each sleeve by way of intake conduits and which after the cooling operation, in the region of the sleeve, is discharged therefrom again by way of discharge conduits.
So that cooling of a large number of sleeves can be carried out simultaneously in a machine which is as compact as possible, carrier plates have been developed, having a plurality of sleeves secured thereto, with fluid conduits extending in the carrier plate in order to pass the cooling fluid, preferably cooling water, from a fluid inlet for the entire carrier plate, in parallel relationship and more or less at the same time to the sleeves through which the fluid flows for the cooling operation, and to take the fluid out of the sleeves again to a fluid outlet.
Known cooling systems however suffer from serious disadvantages. Although the cooling conduits in the individual sleeves and thus also the intake and discharge conduits at the sleeves are of a small cross-section, nonetheless the individual conduit cross-sections add up considerably when there is a relatively large number of sleeves through which fluid is to flow at the same time. In the case of a known carrier plate of for example 144 sleeves, the surface area which is to be supplied with cooling fluid is about 1,800 mm2. In comparison with that consumption surface area there is cross-sectional area of only about 500 mm2 at the fluid inlet. The area which is to be supplied with fluid at the sleeves is therefore disadvantageously about four times as great as the available entry area for the cooling fluid. That signifies a severe pressure drop from the fluid inlet to the sleeve outlet and in the region of the sleeves there is scarcely still any turbulence, due to the flow speeds being lower as a result of that pressure drop. In the absence of turbulence however the cooling action also falls severely. At the same time the carrier plate may suffer from the disadvantage of flooding because impurities settle in the fluid conduits due to the slow flow and the low pressure and are not flushed away. The transfer of heat between the fluid inlet and the fluid outlet is reduced, as a further disadvantage.